In a long-term evolution (LTE) system, a physical downlink control channel (PDCCH) is used to transmit control information, including downlink scheduling information (DL-grant), uplink scheduling information (UL-grant), and control information, etc. Signaling transmitted in the PDCCH is referred to as downlink control information (DCI). A base station multiplexes PDCCHs of all mobile stations in a cell in former several OFDM symbols of a subframe for transmission, and latter OFDM symbols of the subframe are used for transmission PDSCHs of the mobile stations; wherein, a region transmitting the PDCCHs is referred to as a control region, and a region transmitting the PDSCHs is referred to as a data region. Currently, at most 3 OFDM symbols may be used for transmission of PDCCHs, and a typical subframe structure is shown in FIG. 1.
However, in some scenarios, there would be a case where capacity of the PDCCH is limited, that is, the capacity of 3 OFDM symbols cannot meet the scheduling requirement of current mobile stations. In such a case, for example, in LTE Release 11, there exist multiple radio remote headers (RRHs) in a cell at the same time, so as to provide better services to mobile stations in the area. Typical deployment of a cell containing RRHs is shown in FIG. 2. As the transmission power of an RRH is relatively low and the RRHs are spaced apart by a relatively large distance, mobile stations within the coverage of different RRHs may share the same resources; that is, comparatively speaking, in resources of a subframe, the number of mobile stations that may be scheduled in a cell may be greatly increased. Therefore, the number of pieces of scheduling information needs to be transmitted in a subframe will be correspondingly increased, and conventional 3 OFDM symbols may be insufficient for placement of scheduling information of all the mobile stations. If such a problem cannot be solved, scheduling of UE (user equipment) will be reduced, thereby lowering the throughput of the system.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present invention and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present invention.